The present invention relates to a motor control apparatus for inferring the position of a magnetic pole of a synchronous motor rotor and controlling the synchronous motor in accordance with the inferred position of the magnetic pole.
A conventional technology adopted in a motor control apparatus for inferring the position of a magnetic pole of a synchronous motor is disclosed in Japanese Patent Laid-open No. Hei 7-245981.
According to description in Japanese Patent Laid-open No. Hei 7-245981, a component of a current vector or a voltage vector parallel and perpendicular to an alternating voltage vector or an alternating current vector applied to a salient pole synchronous motor is detected. From at least one of the components, a phase difference angle formed by the applied vector and a magnetic flux axis is calculated and the position of a magnetic pole is inferred from the calculated phase difference angle.
This technique offers the benefit that the position of a magnetic pole can be inferred without letting the synchronous motor generate a torque since the alternating voltage is applied to the magnetic flux axis.